Scientists at the University of British Columbia and the University of California, Berkeley have discovered some amazing things while studying fin whales. First, the gulps of some of these baleen whales can take in a volume of water equal to the size of a school bus. These are no small gulps, especially with jaws that can be up to one-fifth their 88 feet body length!
Baleen whale generally have 200-400 overlapping plates hanging from each side of the upper jaw, where you might expect to find teeth. These plates, called baleen, are made of a fingernail-like material called keratin. "During feeding, large volumes of water and food can be taken into the mouth because the pleated grooves in the throat expand. As the mouth closes water is expelled through the baleen plates, which trap the food on the inside near the tongue to be swallowed." (Info from the American Cetacean Society)